I recently bought a 1992 ST185 GT4 (Jap Import). At the time of purchase, I noticed that the CEL (Check Engine Lamp) was not working. The engine started but would not IDLE very well and would cut-out after 5-7 seconds. Whilst trying to drive the car, the engine would struggle to get up through the revs. After 2500 rpm it would drive as it should. I decided to take a chance and buy the car anyway.After I trailored the car home (80 miles) and decided to investigate the why the CEL light was not operating. After checking that the 'gauge' fuse in the footwell (RH) was OK, I proceeded to remove the dash instrument cluster to check the CEL bulb, and as I had suspected, the CEL bulb was missing. (Previous owner told me that he never seen it working, but I guess now he removed it prior selling the car).

So I fitted a new CEL bulb in Instrument Cluster. After turning ON the Ignition (but not starting engine) the CEL was still not working, as it normally would, but as soon as I turned the key to start the engine, the 'Check Engine Light' came on, and stayed on while the engine was running. When I turn the ignition off to stop the engine, and turn it back on again, still the CEL does not come on. It will only come on as soon as I turn the key to start the engine.

If I reset the ECU (Disconnect the battery for 5 mins) and turn on the IGNITION, the CEL may or may not come on. Some times it will and some times it wont.Now, to the weird bit, If I switch off the ignition and connect the TE1 and E1 connectors in the 'Check Connector' Diagnostics port, and turn on the IGNITION, the CEL will light, but will not flash to indicate either normal (blink ON and OFF at 0.5–second intervals) or abnormal operation (irregular blink seq).

At this stage, I suspect that the ECU is faulty and will need to be replaced.

I've read the excellent post/thread by 'Nibbles' ECU Repair -> viewtopic.php?f=2&t=5617and I've since removed the inspected the ECU. I do have Capacitor leakage on the lower PCB board, as per above 'ECU Repair' thread.I've done a MultiMeter Continuity Test on all the nearby tracks and none are damaged/open circuit yet !!!The capacitor itself looks to be well past its Best Before Date, so should I attempt to replace it, or at this stage should be looking at replacing my ECU. I've pictures of the damaged capacitor, can post if thats any help!!

The serial/part number on my ECU is:89661-2B280175000-4811.

Any help would be greatly appreciated.

/Declan

Last edited by vtecdec on Mon Feb 29, 2016 1:36 am, edited 1 time in total.

The capacitors on the Top board looked OK, I didn't notice any capacitors leaking or burned out like the one on the lower board.I've since put the ECU back into the car, however I'd need to have another look at it and the weekend and I'll add photos of the top board to the thread.

Here is a photo of the lower board with the leaking capacitor. I've tested continuity across the Blue and Red tracks, all good. What is the purpose of this capacitor, does it need to be replaced?

Also, here is the Serial/Model of the ECU. Is there a Toyota ECU compatibility chart, ie Will an ECU from a 1994 ST205 function in my car (1992 ST185 JDM). Can an ECU from a ST182/3S-GE be used in a 185/3S-GTE.

It's a later spec 185 a-a ECU. These are quite rare it seems, most are the earlier type.

You will need one the same part No. Although the pinout is very similar to the RC/CS/205 generation the mapping is very different.

As far as I can see, the capacitor on the lower board is decoupling to absorb flyback energy from the idle solenoids. I very much doubt you'd notice much difference if the capacitor was missing, in fact I've seen ecu's with the capacitors failed and running perfectly.

I would put a tenner on the capacitor on the top board having gone and broken the triangular shaped track. These don't tend to leave such a mess on the board (gravity) and the damage is easily missed with just a casual look.

The important thing is to remove the failed capacitors and clean off the corrosive goo using solvent (e.g. white spirit). Find the broken tranks and put links across them, solder in the new capaciors and finally spray with laquer (or ideally conformal coating).

OK, I've looked at this again and you're right ...... the Capacitor on the top ECU has also leaked and appears to have done a lot of damage to the tracks on the PCB. Do you think this repairable from looking that these pictures? I haven't done any work to it yet, I'd like your opinion, before I tackle it. Would you be interested in repairing it for me?

Cheers Chris .... you say "If it's still largely working I'd guess that most of those tracks are probably ok underneath." Thats the problem Chris, there are a number of symptoms. Firstly the "Check Engine Light" is not operating as it should and secondly, its hard to start and when the engine starts but does not IDLE very well and will cut-out after 5-7 seconds, I have to keep the revs up to keep it running. While trying to drive the car, the engine would struggle to get up through the revs. After 2500-3000 rpm it seems ok/normal-ish.

I suppose the first step is to repair the ECU so that we can read (if any) fault codes, its possible that all my problems are related to the leaking capacitors.I'll clean up the tracks around the leaking capacitor to see if there is any real damage and check for continuity across the tracks. It the damage is minimal, I might have a go a repairing it myself, if not I'll post it to you. Do you have the correct capacitors required for the repair?

I'm on the border with Northern Ireland and I've a mate living just across the border in N. Ireland so I could get you post it back to him (might be a cheaper that posting to Eire).

Most of those symptoms are consistent with the one I've experienced personally which was just the single track broken on the top board I've already mentioned.

The tracks that nearly always go are the negative end of the capacitor on the lower board up to the transistor above. Also the triangular track on the top board. Both of these will probably need links. I suspect the other tracks are probably usable provided they are thoroughly cleaned with solvent and then coated with laquer or conformal to stop further corrosion.

Quick Update in my ECU Repair .... I've made some good progress with this.After cleaning up the area around the leaking capacitor I could clearly see that many tracks were damaged/corroded.

Zooming IN on the damaged tracks

We can see that we have damage to tracks numbered 1,2,3,5,6 and 7. Tracks 4, 8 and 9 are good.

After tracing the source/destination points of the damaged tracks on the back of the PCB, I created jumpers and soldered in as follows .....

I also replaced the 2 leaking Capacitors (10µF 50v) on both the TOP and BOTTOM PCB boards that caused the damage to the PCB tracks.

After reinstalling the ECU into the car, the 'Check Engine Light' (CEL) is now working as it should.When I turn ON the ignition, the CEL lamp is ON, and as soon as the engine is started the light goes out.When the engine is switched off, and the Ignition is switched ON again the CEL will come ON again as expected.When I connect the TE1 and E1 connectors in the 'Check Connector' Diagnostics port, and the Ignition is turned ON, the CEL light will blink/flash at a steady pace (2-3 times a second).

So, ECU repair was successful and a huge thanks to Chris aka "Nibbles". Thanks again for your help in steering me in the right direction with this repair.

The Engine is still not running right, I was hoping to get some diagnostic codes after repairing the ECU, but unfortunately the CEL light is not coming ON, nor are Diagnostics Codes visible when connecting the TE1 and E1 connectors in the 'Check Connector' Diagnostics port.

You missed the one track on the top board that I mentioned earlier - the triangular shaped track going to the + of the capacitor. Put a link from capacitor + to the via holes the other end of that track. (do this on the other side of the board).

You missed the one track on the top board that I mentioned earlier - the triangular shaped track going to the + of the capacitor. Put a link from capacitor + to the via holes the other end of that track. (do this on the other side of the board).

Hi Chris, when I removed the leaking capacitor and was able to get a better look at the 'triangular' shaped track, however it was not damaged/corroded, and thus didn't need repairing/jumpers. I did a continuity test from the capacitor (+) to the 2 soldered joints visible to the LH side of the capacitor (above) and it was OK. I did the same on the opposite side too, continuity was good from capacitor (+) to the connect points.

p.s. I can also see track damage to tracks higher up too. Worth checking continuity of these.

Chris, Are you referring to the Tracks I've labelled 1,2 and 3. Or are you talking about the numerous tracks to the top right of the leaking capacitor .... the track that seem to run under the larger semi-conductor chip?